Method of making a pneumatic cord tire



3, 1967 F. J. KOVAC ETAL METHOD OF MAKING A PNEUMATIC CORD TIRE Original Filed Oct. 2, 1965 FIG. 3

INVENTOR. FREDERICK J. KOVAC GROVER W. RYE

United States Patent 3,345,228 METHOD OF MAKING 'A PNEUMATIC CORD TIRE Frederick J. Kovac, Akron, and Grover W. Rye, Cuya- This'is a division of Ser. No. 313,382, filed Oct. 2, 1963, now US. Patent 3,217,778.

This invention relates to pneumatic tires and particularly to a tire containing texturized cord fabric reinforcement.

In conventional cord tire casings, the reinforcement is formed from one or more plies of fabric that girth the tire from bead to bead. The plies are positioned so that the orientation of the cord reinforcement of one ply is angularly disposed with respect to the cord reinforcement of the adjacent ply or plies. It has heretofore also been convention-a1 to form each reinforcement ply with closely spaced, straight parallel oriented cords held in position with a minimum of non-load carrying tie-in fill members. Each of the cord reinforcement members are normally made from a plurality of yarns that are in turn composed of several individual filaments. The conventional tire reinforcement cord is fabricated by twisting a selected number of yarns in one direction. The yarns are then twisted together with a twist opposite that of the twist utilized in the formation of the yarns. The cord thus formed in very stable and lends itself well to providing tensile strength for the ordinary automobile tire.

With the advent of wider low profile and two-ply tires, the cord reinforcement must excel not only in its ability to withstand tensile loads, but also compressive loads. Compressive loads become more significant as the tire becomes more yieldable through lower operating pressures that result in a larger ground contact'area or foot print.

an ultimate breakdown of the load carrying capabilities of the cords. The lack of elasticity of such tire cords detracts from the impact absorbing action and hence the riding characteristics.

The term texturized is used to connote a reinforcement in which the individual fibers or groups of fibers have been purposely bent or deformed from their straight or extruded configuration. The principle behind the manufacture of a texturized or stretch yarn is that the'yarn is held in a crimped or bent position by suitable means while at an elevated temperature and 'on cooling the yarn remains cn'mped. If a texturized yarn is: pulled, the crimps straighten out and the yarn is then capable of withstand ing a tensile load. Whenthe elongating force is removed, the crimps reform and the yarn contracts in length because of memory characteristics that have been imparted to it.

Filamentary material that lends itself well to texturizing can be any artificial thermoplastic organic'substance such as linear polyami'des, linear polyesters such as polyethylene terephthalate, polyacrylonitrile and polyolefins. Non-thermoplastic substances, such as rayon, and staple products, such as cotton, are not considered applicable to the present invention. In some of the thermoplastic materials, such as polyethylene terephthalate, the filaments have been stretched to enhance their crystalline structure, thus resulting'in an extra strong material. In order to insure heat stability, the oriented or stretched filamentary material is heat set at a temperature below that which would destroy the crystallinity previously imparted thereto. In the crimping operation used to produce a texturized yarn, the heat applied is enough to produce a permanent memory, but not enough to destroy the orientation previously created within the yarn.

It is an object of the present invention to provide a reinforced pneumatic tire that contains therein texturized yarns capable of withstanding the tensile loads encountered during operation of the tire, yet possessing enough resilience to absorb the stresses resulting from compressive loads.

It is an additional object of the present invention to incorporate into a pneumatic tire a texturized reinforcement yarn containing a series of undulations that do not result in a twisting of the yarn.

A further object of the invention is to provide a pneumatic tire capable of absorbing a concentrated local deformation without rupturing the carcass.

An additional object of the present invention is to provide a texturized reinforcement yarn that has been heat set in a helical no twist configuration about the longitudinal axis thereof. Another objetc of the invention is to utilize to the fullest extent the physical characteristics of synthetic tire reinforcement.

Conventional cord reinforcement formed by twisting can, result in tensile losses as great as 20%, as will be explained hereinafter. The use of untwisted yarns in a texturized condition results in improved load carrying capabilities because of the better tensile yield obtainable from the reinforcement material.

While some of the more obvious features and characteristics of the present invention have been pointed out above, others will readily be apparent from the following disclosure and claims together with the accompanying drawing in which:

FIG. 1 is a fragmentary perspective view showing a pneumatic tire containing reinforcement as set forth in the present invention; I

' FIG. 2 is an enlarged view showing a texturized group of fibers in the relaxed condition;

FIG. 3 is a view similar to FIG. 2 except that the fibers are fully elongated;

FIG. 4 shows a prior art reinforcement cord of twisted construction and a force diagram of the tensile load carried by the cord;

FIG. 5 is a view showing the configuration of the yarn when in position within the cured tire.

Referring to the drawing, FIG. 1 shows a perspective view of a pneumatic tire 10 in which a portion of the tread stock 11 and sidewall rubber 12 have been removed in order to more clearly show the tire reinforcement layers 13, 14, 15 and 16. A conventional 4-ply tire construction is shown; however, the reinforcement of this invention would work equally well with other types of tire construction. As tire 10 encounters a rough object, such as a rock, the tread stock 11 absorbs the cutting tendency of -the object'but the tire reinforcement layers must bend around the object that is deforming the toroidal shape of the tire. As the circumferential convexity of the tire is disrupted, 'a depression or concavity is formed around the indenting object. The points of contraflexure between the concave and convex surfaces, as is typical in pressure vessels, are the areas of greatest stress reversals. A tire reinforcement ideally is in a state of tension coupled with bending during tire usage. The absorption of rough blows to the tire carcass, particularly in the footprint, causes greatly increased compressive and tensile stresses to be induced in the tire reinforcement. Since the bending stresses are ever-present in a moving tire, the additional compressive and tensile stress caused by a blow adds to the compressive and tensile components thereof, thuscausing failure of the individual filaments of which the tire reinforcement is composed. The ordinary twisted cord reinforcement utilized in tires can withstand direct tensile loads without serious detrimental effect. When similar compressive loads are imposed upon a reinforcement cord plied from twisted yarns, improper pantographing occurs and the fatigue life is sharply reduced; hence, early failure results.

FIG. 2 is an enlarged view in which the texturized tire reinforcement is shown. Yarn 30 is formed from a group of individual filaments 31. The group of filaments are then heat set in .a helically crimping operation that produces turns 32. The overall diameter W of turns 32 is preferably two to three times the diameter D of yarn 30. The texturizing of the yarn 30 can be accomplished by feeding the thermoplastic yarn from a supply source into a heater, then through a false twister to a suitable withdrawal and/ or collection means. Crimping and false twisting of thermoplastic threads is well-known in the art; therefore, space will not be devoted to a description of the apparatus by which such results can be achieved.

. Yarn 30'is preferably helical in shape or configuration similar to that of a cork-screw. The yarn can also be formed without a helical configuration. For example, a series of well-defined sinusoidal crimps will work equally well. Additionally, yarn 30 has a substantially constant pitch P as shown in FIG. 2.

FIG. 3 shows the yarn of FIG. 2 in the fully elongated condition. The helical false twist is shown completely removed without rotation of the ends taking place. In the unstretched condition of FIG. 3, yarn 30 can carry the tensile load imposed upon it when incorporated within a pneumatic tire. Each individual filament is aligned parallel to the direction of its load carrying path. This is not so if the yarn is in the twisted condition when subjected to an axial load.

FIG. 4 by contrast shows a prior art cord 40 that is of twisted construction. The individual filaments 41 are not aligned axially with respect to the axial direction, but rather areoriented at some angle thereto such as A. The tensile load T represents the tension that can be carried by the filaments. It is then quite obvious that the load carrying ability X of the cord is less than tensile load T. An additional force Y is necessary to balance the force diagram. Force Y can introduce shear stresses which are detrimental to the overall fatigue life of the cord.

FIG. 5 represents the position of yarn 30 as it is found in the completed pneumatic tire. The attitude of yarn 30 is between the fully relaxed texturized yarn of FIG. 2 and the completely elongated yarn of FIG. 3.

A complete fabric ply within a tire such as has embedded therein closely spaced yarns lying in the plane of the ply'that extends helically from one end of the strip to the other. The fabric including the texturized yarns can be cut diagonally to form plies for tire building. The tire carcass can be laid in plies upon a drum in the con ventional tire building manner. The plies containing yarns are ideally placed one upon the other in the tire carcass with the yarns of adjacent plies opposite in angularity as is shown in FIG. 1.

When the drum-built uncured tire containing the yarns of this invention is expanded during the cure cycle the yarns will become partially elongated as shown in FIG. 5. The resulting finished pneumatic tire is therefore inherently elastic in that yarns 30 can, upon slightly more elongation, develop their load carrying capabilities and in those instances when compressive loads are present the yarns can compress without undue damage thereto. Since thermoplastic synthetic fibers have a memory, the yarn will have a tendency to return to its original unstressed texturized condition. This feature insures a greater fatigue life, primarily because the heretofore compressive loads could not be distributed along the cord reinforcement without rupturing the individual filaments of which the reinforcement cord was composed.

, While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

We claim:

1. The method of making a pneumatic tire comprising in combination the steps of (l) forming a filamentary reinforcement material into a yarn;

(2) crimping the yarn in an undulating pattern thereby inducing a memory in said reinforcement yarn;

(3) positioning the crimped yarns in a tire reinforcement layer so that the longitudinal axis of adjacent yarns are substantially parallel;

(4) building a tire carcass in cylindrical form and including contiguous therewith at least one reinforcement layer containing crimped yarns;

(5 expanding the cylindrical tire carcass into toroidal form wherein the crimped yarns of said reinforcement layer are elongated, thus increasing the pitch of the yarn undulations; and

(6) curing the toroidal shaped tire so that the reinforce- I ment material is firmly adhered to the adjacent elastomeric carcass material, thus providing a tire containing reinforcement yarns that can elongate to assume a tensile load and can withstand compressive loads by contracting in the direction of the original crimping.

2. The method of making a pneumatic tire comprising in combination the steps of (1) forming a plurality of continuous thermoplastic filaments into an untwisted reinforcement yarn;

(2) crimping the thermoplastic reinforcement yarn by the application of heat so that it assumes an undulating'constant pitch pattern, thus imparting a retainable memory in the reinforcement yarn;

. (3) positioning the crimped yarns in an unvulcanized elastomeric layer suitable for tire building in such manner that the longitudinal axis of said yarns are substantially parallel to each other;

(4) building a pneumatic tire carcass in cylindrical form and including as an integral part thereof at least one reinforcement layer containing the crimped thermoplastic crimped reinforcement yarns;

(5) expanding the cylindrical uncured tire carcass into toroidal form thus increasing the length of the yarns so that residual crimping remains; and

-(6) curing the toroidal shaped tire wherein the reinforcement material is firmly adhered to the adjacent elastomeric carcass material, thus providing a pneumatic tire in which the individual reinforcement yarns can elongate to assume a tensile load and can withstand compressive loads by contracting in the direction of the original crimping.

3. The method of making a pneumatic tire comprising in-com'bination the steps of f (l) forming a plurality of continuous thermoplastic filaments into an untwisted reinforcement yarn;

(2) crimping the thermoplastic reinforcement yarn until it assumes a helically oriented constant pitch =-pattern thus imparting a retairiable memory in the reinforcement yarn;

(3) positioning the crimped yarns in an unvulcanized elastomeric layer suitable for tire building so that the longitudinal axis of the yarns are substantially parallel to each other;

(4) building a pneumatic tire carcass in cylindrical form .and including as an integral part thereof at References Cited UNITED STATES PATENTS Axline 16176 Hoff 156-110 Jahant 152356 Appleton et a1. 161179 Hulswit et a1 156-110 Kitson et a1. 18-48 Heberlein 16176 X Correll et al 156l48 X EARL M. BERGERT, Primary Examiner.

C. B. COSBY, Assistant Examiner. 

1. THE METHOD OF MAKING A PNEUMATIC TIRE COMPRISING IN COMBINATION THE STEPS OF (1) FORMING A FILAMENTARY REINFORCEMENT MATERIAL INTO A YARN; (2) CRIMPING THE YARN IN AN UNDULATING PATTERN THEREBY INDUCING A MEMORY IN SAID REINFORCEMENT YARN; (3) POSITIONING THE CRIMPED YARNS IN A TIRE REINFORCEMENT LAYER SO THAT THE LONGITUDINAL AXIS OF ADJACENT YARNS ARE SUBSTANTIALLY PARALLEL; (4) BUILDING A TIRE CARCASS IN CYCLINDRICAL FORM AND INCLUDING CONTIGUOUS THEREWITH AT LEAST ONE REINFORCEMENT LAYER CONTAINING CRIMPED YARNS; (5) EXPANDING THE CYLINDRICAL TIRE CARCASS INTO TOROIDAL FORM WHEREIN THE CRIMPED YARNS OF SAID REINFORCEMENT LAYER ELONGATED, THUD INCREASING THE PITCH OF THE YARN UNDULATIONS; AND (6) CURING THE TORODIAL SHAPED TIRE SO THAT THE REINFORCEMENT MATERIAL IS FIRMLY, ADHERED TO THE ADJACENT ELASTOMERIC CARCASS MATERIAL, THUS PROVIDING A TIRE CONTAINING REINFORCEMENT YARNS THAT CAN ELONGATE TO ASSUME A TENSILE LOAD AND CAN WITHSTAND COMPESSIVE LOADS BY CONTACTING IN THE DIRECTION OF THE ORGINAL CRIMPING. 